The objective of this project is to establish the complete sequence of a number of oligosaccharide moieties present on serum and membrane glycoproteins, and to utilize these fully defined structures as probes for examination of lectin specificity. The complete structures of the complex oligosaccharides of fetuin and J chain have been determined and those present on ceruloplasmin and on IgD myeloma protein are presently being examined. A new method for examining lectin specificity has been established utilizing iodinated glycopeptides and plant lectins such as concanavalin A as a model system. Studies of the receptor specificity of the human, hepatocyte galactose-binding receptor are being carried out using a large number of iodinated glycopeptides. These studies will permit us to evaluate the basis of specificity of the receptor for oligosaccharides and will also permit examination of receptor function in intact cells with well characterized monovalent probes.